A large variety and number of communication devices are currently available. For example, many consumers carry a wireless (e.g., a cellular) telephone that is used in addition and as a complement to land line telephones at the user's workplace and home. In addition, different communication technologies may be used to provide connections to communication endpoints. For example, in addition to plain old telephones (POTs) interconnected to the public switched telephony network (PSTN), telephony communications can be established using Internet Protocol (IP) soft or hard phones. Each of these different types of communication devices and communication technologies have advantages and disadvantages relative to other technologies. For instance, cellular telephones allow a user to change their location while carrying on a telephone call. Therefore, a cellular phone may be preferred to a landline when the user wants to maintain a telephone call while changing locations. However, cellular telephones are often more expensive to use than landline telephones. Therefore, if a user does not need to be able to change location, a landline telephone may be preferred.
Because of the different relative advantages and disadvantages of different communication devices and associated communication technologies, it would be desirable to allow for in-progress telephone calls or other active communication sessions to be transferred between devices. Currently, call forwarding and conferencing capabilities are supported by many communication systems. However, transferring a call using call forwarding or conferencing requires that the number of the communication device to which the call is to be forwarded or that is to be added to a call be dialed. In addition, conventional systems can either perform call transfer or call forwarding with respect to a call, but not both. Also, transferring a call from a cellular phone to a land line phone is usually not supported. In addition, a user must wait until a call is transferred, which takes time. As a further disadvantage of conventional systems, a call involving a cellular telephone that is forwarded can be disconnected if the cellular telephone battery dies, enters a location that does not have wireless network coverage, or enters an area in which it is roaming. Therefore, such systems are too cumbersome to use to transfer calls from one communication device of a user to another communication device of the user for purposes such as convenience or a more favorable billing plan.